/*
 *
 * Copyright (c) 2003 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA"
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 */

package net.jxta.impl.util.pipe.reliable;

/**
 * A basis for any flow control module to be plugged into
 * ReliableOutputStream.  Synchronization can is assumed to be
 * provided externaly. However all implementations are required to
 * allow the getRwindow() method to be called at any time without
 * synchronization.
 */

public abstract class FlowControl {

    /**
     * Returns the rwindow size that this flow control module suggests to use
     * at this point in time.
     */
    public abstract int getRwindow();

    /**
     * Indicates that a new ack message is being processed.
     */
    public void ackEventBegin() {
    }

    /**
     * Invoked for each packet that is believed to have been received
     * per the current ack message.
     *
     * @param seqnum The sequence number of the received packet.
     */
    public void packetACKed(int seqnum) {
    }

    /**
     * Invoked for each packet that is believed to have been lost
     * per the current ack message.
     *
     * @param seqnum The sequence number of the missing packet.
     */
    public void packetMissing(int seqnum) {
    }

    /**
     * Concludes rwindow update for this ackEvent. That's where all the
     * smarts are. A number of externally computed parameters must be
     * passed.
     *
     * @param rQSize the last known value of the remote queue size.
     * @param aveRTT the latest estimate of the average RTT.
     * @param lastRTT the RTT inferred from the most recent ACK message.
     * @return int the new recommended value for rwindow.
     */

    public abstract int ackEventEnd(int rQSize, long aveRTT, long lastRTT);
}
